The 27-year-old from Syria who allegedly confessed to police that he was a member of ISIS will appear before an investigative magistrate after asking for a deferral on Monday.
He appeared in court on Monday morning wearing a bulletproof vest and accompanied by officers from the counterterrorism service and asked for a lawyer to be appointed on his behalf so that he can appear again on Tuesday.
He was arrested last Wednesday at the Eleonas migrant facility in Athens, where he had been staying.
He allegedly confessed to counterterror officials that he had been an ISIS member and that he was in a video showing the execution of four hostages by ISIS in 2014.
He reportedly claimed that he left the ranks of ISIS in 2018, when he traveled to Greece with his wife and their five children.
He faces criminal charges of joining a terrorist organization and direct assistance in homicides and acts of terrorism.
The case file is expected to include evidence gleaned from mobile phones and other electronic devices found in the accommodation where he lived.